In waste water treatment and drinking water preparation, in addition to disinfection, the reduction of disinfection by-products, the removal of nitrogen and phosphorus and the elimination of odours and flavourings, the elimination of micro-contaminations is becoming increasingly important.
Micro-contaminations are intended to be understood to be organic substances which occur in waters at concentrations in the range from a few nanograms to micrograms per liter and which at these concentrations can already influence the sequence of basic biochemical processes in nature. These include, on the one hand, many synthetic substances, such as medicaments, materials with biocidal properties, food additives, contents of cosmetics or cleaning agents, etcetera, but also materials of natural origin, such as, for example, hormones.
US 2012/0080374 A1 discloses a method for water treatment in which micro-contaminations are for the most part removed with an ozonisation operation and subsequent bioreactors or converted into non-problematic products. A control system of the method is not described.
DE 43 08 159 A1 discloses a method for decomposing the COD (Chemical Oxygen Demand) load in waste water in which an oxidation step with ozone is arranged upstream of a biological filter. The oxidation by means of ozone leads for the most part to a direct decomposition of the COD load and the remaining COD is changed in terms of its structure by the reactive ozone so that it can be decomposed by the biological filter. A control system of the waste water treatment is also not disclosed therein.
WO 2014/025478 A1 discloses a method for controlling a waste water treatment installation having an ozonisation action and a biological filter. In the discharge downstream of the filter, the TOC (Total Organic Carbon) of the waste water is measured using a sensor which detects the spectral absorption of electromagnetic radiation in the UV spectrum and/or in the visible spectrum and by means of an additional measurement of the oxidation/reduction potential. Using these two values, the ozone supply and where necessary the oxygen supply of the biological filter is/are subsequently controlled in order to obtain the desired water quality.
A significant cost factor of the above-mentioned installation combination of ozonisation and biological filters is the energy consumption of the ozone generator and the oxygen production. The ozone supply is consequently intended to be controlled in such a manner that in each case only the quantity of ozone required for the cleaning objective is produced and introduced. Additional factors which influence operating costs involve the operation of the biologically active filter (backwash intervals). It is therefore desirable with respect to optimisation of the costs to operate the installation combination in the most efficient manner possible.